The invention relates generally to lamps and, more particularly, techniques to reduce the potential for thermal stresses and cracking in high intensity discharge (HID) lamps.
High-intensity discharge lamps are often formed from a ceramic tubular body or arc tube that is sealed to one or more end structures. Unfortunately, various stresses may arise from the sealing process, the interface between the joined components, and the materials used for the different components. For example, the component materials may have different mechanical and physical properties, such as different coefficients of thermal expansion (CTE), which can lead to residual stresses and sealing cracks. These potential stresses and sealing cracks are particularly problematic for high-pressure lamps.
HID lamps are typically assembled and dosed in a dry box, which includes a furnace to facilitate hot sealing with temperatures reaching about 1500 degrees centigrade or higher. Unfortunately, the dry box complicates the assembly of HID lamps due to the closed environment. In addition, the furnace typically subjects the dose materials to high temperatures, thereby limiting the operational pressure of the dose materials.